Hotkey of Erase in Texture Paint?
I don't use the eraser on my tablet(mine doesn't come with one) but Texture Paint mode has a mix mode in the brush controls called 'Erase Alpha', and that generally does what you expect in that it seems to erase the paint - BUT if you also then switch to 'Add Alpha', you can then recover what you thought was erased. 

I don't know about setting up an operator to swap to the Erase Alpha mix mode and back to the last used brush mix mode, but that might be possible, and then you woudl have to map it to the eraser input. I use an add-on called EZ Paint that enables me to toggle erase/add alpha with a short cut key, but that isn't what you are looking for.